Coatings for medical devices comprising a therapeutic agent and a metallic material

ABSTRACT

The invention relates generally to an implantable medical device for delivering a therapeutic agent to the body tissue of a patient, and a method for making such a medical device. In particular, the invention pertains to an implantable medical device, such as an intravascular stent, having a coating comprising a first coating composition comprising a therapeutic agent and, optionally, a polymer; and a second coating composition comprising a metallic material.

FIELD OF THE INVENTION

The invention relates generally to implantable medical devices for delivering a therapeutic agent to the body tissue of a patient, and methods for making such medical devices. In particular, the invention pertains to implantable medical devices, such as intravascular stents, having a coating comprising a first coating composition comprising a therapeutic agent and a second coating composition comprising a metallic material.

BACKGROUND OF THE INVENTION

Medical devices have been used to deliver therapeutic agents locally to the body tissue of a patient. For example, intravascular stents comprising a therapeutic agent have been used to locally deliver therapeutic agents to a blood vessel. Often such therapeutic agents have been used to prevent restenosis. Examples of stents comprising a therapeutic agent include stents that comprise a coating containing a therapeutic agent for delivery to a blood vessel. Studies have shown that stents having a coating with a therapeutic agent are effective in treating or preventing restenosis.

Even though medical devices having a coating with a therapeutic agent are effective in preventing restenosis, many coated medical devices, in addition to being coated with a therapeutic agent, are also coated with a polymer. The benefits of using a polymer in such coatings include easier loading of therapeutic agents onto the surface of a medical device and the ability to control or regulate the rate of release of the therapeutic agent.

However, the use of polymers in medical device coatings can also have some disadvantages. For example, depending on the type of polymer used to coat the medical device, some polymers can cause inflammation of the body lumen, offsetting the effects of the therapeutic agent. Additionally, some polymers may also cause thrombosis.

Accordingly, there is a need for coatings for a medical device that prevent or at least reduce the disadvantages associated with polymer coatings, such as inflammation caused by contact with the body lumen. Moreover, there is a need for a coating for medical devices that can control or regulate the release rate of a therapeutic agent without the use of polymer coatings. There is also a need for methods of making such medical devices.

SUMMARY OF THE INVENTION

These and other objectives are accomplished by the present invention. The present invention provides a medical device, such as an implantable, intravascular stent comprising a coating. The coating is designed to eliminate or at least reduce the amount of polymer contact with the body tissue, such as a body lumen, while still providing a suitable release rate of the therapeutic agent. The coating comprises a first coating composition comprising a therapeutic agent and a second coating composition comprising a metallic material. Optionally, the first coating composition can further comprise a polymer.

The coating can comprise a first coating composition comprising a therapeutic agent, disposed on the surface of a medical device; and a second coating composition, which comprises a metallic material and which is substantially free of any polymer, disposed on at least a portion of the first coating composition. Metallic materials are materials containing a metal including but not limited to, metals alloys and oxides. As used herein and unless otherwise defined the phrase “substantially free of any polymer” means having less than or equal to 50% of polymer by volume of the composition. With such coatings, polymer contact with the body lumen is reduced or eliminated.

For example, the present invention is directed to an implantable intravascular stent comprising: (a) a stent sidewall structure having a surface; and (b) a coating comprising: (i) a first coating composition comprising a therapeutic agent disposed upon at least a portion of the surface of the stent sidewall structure, wherein the first coating composition, when disposed on the portion of the surface of the stent sidewall structure, has an outer surface; and (ii) a second coating composition comprising a metallic material disposed on at least a portion of the first coating composition, wherein the second coating composition is substantially free of any polymer when applied to the portion of the first coating composition; and wherein after the second coating composition is applied to the portion of the first coating composition the second coating composition comprises an outer surface and a plurality of pores, in which the pores extend from the outer surface of the first coating composition to the outer surface of the second coating composition. In certain embodiments of the present invention the second coating composition is disposed on less than the entire outer surface of the first coating composition. Additionally, the second coating composition can also be further disposed on a portion of the surface of the stent sidewall structure.

The stent sidewall structure can be an abluminal surface or an adluminal surface. In certain embodiments, the coating is disposed on at least a portion of the abluminal surface. In other embodiments, the first coating composition is disposed on at least a portion of the adluminal surface and the second coating composition is disposed on at least a portion of the first coating composition disposed on the adluminal surface. In still other embodiments, the first coating composition is disposed on at least a portion of the adluminal surface and the adluminal surface is free of the second coating composition.

Additionally, the stent sidewall structure can comprise a plurality of struts wherein the surface of the stent sidewall structure is the abluminal surface or adluminal surface of at least one of the struts. When the stent sidewall structure comprises a plurality of struts, the coating can be disposed on at least a portion of the abluminal or adluminal surface of at least one of the struts. For example, the present invention is directed to an implantable intravascular stent comprising: (a) a stent sidewall structure comprising a plurality of struts each having an abluminal surface and an adluminal surface (b) a first coating disposed on the abluminal surface of at least one strut comprising: (i) a first coating composition comprising an anti-restenosis agent disposed upon at least a portion of the abluminal surface of the strut, wherein the first coating composition, when disposed on the portion of the surface of the abluminal surface of the strut, has an outer surface; and (ii) a second coating composition comprising a metallic material disposed on at least a portion of the first coating composition, wherein the second coating composition is substantially free of any polymer; and wherein after the second coating composition is applied to the portion of the first coating composition the second coating composition comprises an outer surface and a plurality of pores, in which the pores extend from the outer surface of the first coating composition to the outer surface of the second coating composition; and (c) a second coating disposed on at least a portion of the adluminal surface of the at least one strut comprising the first coating composition.

In certain embodiments, the first coating composition is disposed on at least a portion of the adluminal surface of at least one of the struts and at least a portion of the adluminal surface of at least one of the struts is free of the second coating composition. In other embodiments, the first coating composition is disposed on at least a portion of the adluminal surface of at least one of the struts and the second coating composition is disposed on at least a portion of the first coating composition that is disposed on the adluminal surface.

In certain embodiments, the stent sidewall structure can further comprise a plurality of openings therein. When the stent sidewall structure has a plurality of openings, the first and second coating compositions can conform to the stent sidewall structure to preserve the openings in the stent sidewall structure. For example the present invention includes an implantable intravascular stent comprising: (a) a stent sidewall structure comprising (1) a plurality of struts each having an abluminal surface and an adluminal surface, and (2) openings in the stent sidewall structure; (b) a first coating disposed on the abluminal surface of at least one strut comprising: (i) a first coating composition comprising an anti-restenosis agent disposed upon at least a portion of the abluminal surface of the strut, wherein the first coating composition, when disposed on the portion of the surface of the abluminal surface of the strut, has an outer surface; and (ii) a second coating composition comprising a metallic material disposed on at least a portion of the first coating composition, wherein the second coating composition is substantially free of any polymer; and wherein after the second coating composition is applied to the portion of the first coating composition, the second coating composition comprises an outer surface and a plurality of pores, in which the pores extend from the outer surface of the first coating composition to the outer surface of the second coating composition; and (c) a second coating disposed on at least a portion of the adluminal surface of the at least one strut comprising the first coating composition, wherein the adluminal surface of the at least one strut is free of the second coating composition; and wherein the first and second coatings conform to the stent sidewall structure to preserve the openings therein.

Also the present invention is directed to an implantable intravascular stent comprising: (a) a stent sidewall structure having a surface; and (b) a coating comprising (i) a first coating composition comprising a therapeutic agent disposed upon at least a portion of the surface of the stent sidewall structure wherein the first coating composition has a first thickness; and (ii) a second coating composition comprising a metallic material disposed upon at least a portion of the surface of the stent sidewall structure, wherein the second coating composition has a second thickness and is substantially free of any polymer; and wherein the first thickness of the first coating composition is not greater than the second thickness of the second coating composition. The first coating composition can also further comprise a polymer.

In certain embodiments, the second thickness of the second coating composition can be greater than the first thickness of the first coating composition. Alternatively, the first thickness of the first coating composition can be equal to the second thickness of the second coating composition. Moreover, the second coating composition can be disposed adjacent to the first coating composition on the surface of the stent sidewall structure.

In any of the embodiments described above, the first thickness of the first coating composition can be about 1 micron to about 30 microns and the second thickness of the second coating composition can be about 0.1 microns to about 50 microns.

The therapeutic agent in the first coating composition can comprise an agent that inhibits smooth muscle cell proliferation. The therapeutic agent in the first coating composition can also comprise an anti-thrombogenic agent, anti-angiogenesis agent, anti-proliferative agent, antibiotic, anti-restenosis agent, growth factor, immunosuppressant or radiochemical. For example the therapeutic agent can comprise paclitaxel, sirolimus, tacrolimus, pimecrolimus, everolimus or zotarolimus.

Additionally, the first coating composition further comprises at least one polymer. Suitable polymers include, but are not limited to, styrene-isobutylene copolymers, polylactic acid and poly(methylmethacrylate-butyl acrylate-methyl methacrylate).

The metallic material of the second coating composition can be selected from the group consisting of stainless steel, nickel, titanium, chromium and alloys thereof.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be explained with reference to the following drawings.

FIG. 1 shows a cross-sectional view of an embodiment of a coating disposed on at least a portion of a medical device.

FIG. 2 shows a cross-sectional view of another embodiment of a coating disposed on at least a portion of a medical device.

FIG. 3 shows a portion of a medical device that is suitable for use in the present invention.

FIG. 4 shows a cross-sectional view of a stent.

FIG. 4 a shows a cross-sectional view of a strut of a stent having a coating thereon.

FIG. 4 b shows a cross-sectional view of another embodiment of a strut of a stent having a coating thereon.

FIG. 5 shows a perspective view of an embodiment of a coating disposed on at least a portion of a stent.

FIG. 6 shows a perspective view of another embodiment of a coating disposed on at least a portion of a stent.

FIG. 7 shows a perspective view of yet another embodiment of a coating disposed on at least a portion of a stent.

FIG. 8 shows a perspective view of yet another embodiment of a coating disposed on at least a portion of a stent.

FIG. 9 shows a cross-sectional view of another embodiment of a coating disposed on at least a portion of a medical device.

FIG. 10 shows a cross-sectional view of yet another embodiment of a coating disposed on at least a portion of a medical device.

FIG. 11 shows a cross-sectional view of yet another embodiment of a coating disposed on at least a portion of a medical device.

DETAILED DESCRIPTION

The present invention is directed to a medical device comprising a coating comprising a first coating composition containing a therapeutic agent and optionally a polymer. The medical device also includes a second coating composition containing a metallic material and is substantially free of any polymer.

In certain embodiments, the coating comprises a first coating composition comprising a therapeutic agent disposed on the surface of the medical device and a second coating composition comprising a metallic material disposed on the first coating composition. The second coating composition is substantially free of any polymer. Also, after the second coating composition is disposed on the first coating composition, wherein the second coating composition comprises a plurality of pores that extend from the outer surface of the first composition to the outer surface of the second coating composition.

FIG. 1 shows a cross-sectional view an embodiment of a coating disposed on at least a portion of a medical device such as a stent. In this embodiment, medical device 10 has a surface 12 and a coating 20. Coating 20 includes a first coating composition 22 comprising a therapeutic agent 30 disposed on at least a portion of the surface 12 of the medical device 10. When disposed on the surface 12, the first coating composition 22 has an outer surface 22 a. The coating also includes a second coating composition 24 disposed on at least a portion of the first coating composition 22. The second coating composition 24 comprises a metallic material and is substantially free of any polymer. The second coating composition 24 can be disposed on a portion of or the entire first coating composition 22.

As shown in FIG. 1, the second coating composition 24 after being applied to the first coating composition 22 has an outer surface 24 a and also has a plurality of pores 42. At least some of the pores 42 extend from the outer surface 22 a of the first coating composition 22 to the outer surface 24 a of the second coating composition 24. The pores 42 can be partially or completely filled with the first coating composition 22. In either case having the pores that extend from the outer surface 22 a of the first coating composition 22 to the outer surface 24 a of the second coating composition 24 allows the therapeutic agent 30 to be released from the first coating composition 22 underlying the second coating composition 24. Additionally, having pores 42 that allow for fluid communication between the outer surfaces 22 a and 24 a can aid in vascularization, provide long term non-inflammation and minimize or eliminate thrombosis. Furthermore, some or all of the pores 42 in the second coating composition 24 can be interconnected to other pores 42 within the second coating composition 24. In some embodiments, the pores 42 may be disposed in a desired pattern.

In addition, the pores 42 in the second coating composition 24 may have any shape. For example, the pores 42 can be shaped like channels, void pathways or microscopic conduits, spheres or hemispheres. Additionally, the pores 42 in the second coating composition 24 may have any size or range of sizes. In some instances, the pores 42 can be micropores or nanopores. Also, in some embodiments, it may be preferable that the width or diameter of the pores 42 is between about 1 nm and about 10 μm.

The size of the pores 42 can also be used to control the release rate of the therapeutic agent 30. For example, pores 42 having a larger width will allow the therapeutic agent 30 to be released more quickly than pores 42 with a smaller width. Also, the number of pores 42 in the second coating composition 24 can be adjusted to better control the release rate of the therapeutic agent 30. For example, the presence of more pores 42 per unit volume or weight of the second coating composition 24 can allow for a higher release rate of the therapeutic agent 30 than a material having fewer pores 42 therein.

In other embodiments, the coating comprises a first coating composition comprising a therapeutic agent and a polymer disposed on the surface of a medical device and a second coating composition comprising a metallic material disposed on the first coating composition. The second coating composition is substantially free of any polymer. Also, the after the second coating composition is disposed on the first coating composition, the second coating composition comprises a plurality of pores that extend from the outer surface of the first composition to the outer surface of the second coating composition.

FIG. 2 shows a cross-sectional view of another embodiment of a coating disposed on at least a portion of a surface of a medical device. In this embodiment medical device 10 has a surface 12 and a coating 20. Coating 20 has a first coating composition 22 comprising a therapeutic agent 30 and a polymer 32 disposed on the surface 12 of the medical device 10. The first coating composition 22 when disposed on the surface 12 has an outer surface 22 a. A second coating composition 24 comprising a metallic material 40 is disposed on at least a portion of the first coating composition 22. As shown in FIG. 2, the second coating composition 24, when applied on the first coating composition 22, has an outer surface 24 a and a plurality of pores 42. Like FIG. 1, the pores 42 extend from the outer surface 22 a of the first coating composition 22 to the outer surface 24 a of the second coating composition 24.

As shown in FIGS. 1 and 2, the first and second coating compositions can be disposed on the surface of a medical device in the form of layers. The coating can comprise one layer of each of the first and second coating compositions, as shown in FIGS. 1 and 2. However, more than one layer of each of the first and second coating compositions can be disposed on the surface of a medical device.

In other embodiments, the first coating composition disposed on the surface of medical device in a layer can have a thickness of about 1 micron to about 30 microns or about 1 micron to about 10 microns. Preferably, the first coating composition can have a thickness of about 3 microns to about 15 microns or about 0.8 microns to about 3.5 microns. In some instances, a relatively thicker layer may be preferred to incorporate greater amounts of the therapeutic agent. In addition, a relatively thicker layer may allow a greater amount of a therapeutic agent to be released over time.

The second coating composition comprising a metallic material, when disposed on the first coating composition, can have a thickness of about 0.1 micron to about 30 microns. Preferably, the second coating composition comprising a metallic material, when disposed on the first coating composition, can have a thickness of about 1 micron to about 10 microns. In addition, a relatively thicker film may allow the therapeutic agent to be released more slowly over time.

For the second coating composition, suitable metallic materials include any material that includes a metal such as, but not limited to metals, metal alloys or metal oxides that are biocompatible. Such metallic materials include, but are not limited to, metals and alloys based on titanium (such as nitinol, nickel titanium alloys, thermo-memory alloy materials); stainless steel; tantalum; tungsten; molybdenum; nickel-chrome; or certain cobalt alloys including cobalt-chromium-nickel alloys such as Elgiloy® and Phynox®; PERSS (Platinum EnRiched Stainless Steel) and Niobium. Metallic materials also include clad composite filaments, such as those disclosed in WO 94/16646. Preferred, metallic materials include, platinum enriched stainless steel and zirconium and niobium alloys. Additionally, combinations of more than one metal or alloy can be used in the coatings of the present invention.

In some embodiments, the metallic material comprises at least 5%, at least 10%, at least 20%, at least 30%, at least 40%, at least 50%, at least 60%, at least 70%, at least 80%, at least 90%, at least 95%, at least 97%, at least 99% or more by weight of the second coating composition. Preferably, the metallic material is about 1% to about 80% by weight of the first coating composition. More preferably, the metallic material is about 50% to about 100% by weight of the second coating composition.

The second coating composition is substantially free of any polymer, i.e. contains less than about 50% of polymer by weight of the second coating composition. In some embodiments, the second coating composition is free of any polymer.

The coating can be disposed on the entire surface of the medical device or the coating can be disposed on a portion of the medical device. For example, if a medical device, such as a stent, that has an abluminal surface, i.e. the surface that contacts the body tissue, and an adluminal surface i.e. the surface that faces the lumen of the stent and is opposite the abluminal surface, the coating can be disposed on the abluminal surface while the adluminal surface can be free of the coating.

FIG. 3 shows an example of a portion of a stent that is suitable for use in the present invention that has an abluminal and adluminal surface. FIG. 3 shows an implantable intravascular stent 50 comprising a sidewall 52 which comprises a plurality of struts 60 and openings 55 in the sidewall 52. Generally, the openings 55 are disposed between adjacent struts 60. Also, the sidewall 52 may have a first sidewall surface 56 and an opposing second sidewall surface, which is not shown in FIG. 3. The first sidewall surface 56 can be an abluminal surface or outer sidewall surface, which faces the body tissue when the stent is implanted, or an adluminal surface or inner sidewall surface, which faces away from the body tissue. Likewise, the second sidewall surface can be an abluminal surface or an adluminal surface.

In certain embodiments, when the medical device, such as a stent, has a sidewall structure with openings therein it is preferable that the first coating composition and second coating composition disposed on the surface medical device, conform to the sidewall structure of the medical device so that the openings in the sidewall structure are preserved, e.g. the openings are not entirely or partially occluded with coating material.

FIG. 4 shows a cross-sectional view of an intravascular stent 100 that comprises a plurality of struts 105 and a lumen 130. The struts 105 each comprise an abluminal surface 110, which faces away from the lumen 130, and contact the body tissue, such as a blood vessel, when the stent 100 is implanted. The struts 105 each comprise an adluminal surface 120, which faces the lumen 130 when the stent 100 is implanted.

FIGS. 4 a and 4 b show two embodiments where the struts of the stent 100 of FIG. 4 include the coatings of the present invention. In particular, FIG. 4 a shows an embodiment where the first coating composition 22 is disposed on at least a portion of the abluminal surface 12 a and the adluminal surface 12 b of a strut 105. The first coating composition 22 comprises a therapeutic agent 30 and optionally a polymer. A second coating composition 24 comprising a metallic material 40 is disposed on at least a portion of the first coating composition 22 that is disposed on the abluminal surface 12 a and the adluminal surface 12 b of the strut 105. The second coating composition 24 when applied on the first coating composition 22 has an outer surface 24 a and a plurality of pores 42. The pores 42 extend from the outer surface 22 a of the first coating composition 22 to the outer surface 24 a of the second coating composition 24.

FIG. 4 b shows an embodiment where the first coating composition 22 is disposed on at least a portion of the abluminal surface 12 a and the adluminal surface 12 b of a strut 105. The first coating composition 22 comprises a therapeutic agent 30 and optionally a polymer. A second coating composition 24 comprising a metallic material 40 is disposed only on at least a portion of the first coating composition 22 that is disposed on the abluminal surface 12 a. The second coating composition 24 is not disposed on the portion of the first coating composition 22 that is disposed on the adluminal surface 12 b of the strut 105. Like FIG. 4 a, the second coating composition 24 when applied on the first coating composition 22 has an outer surface 24 a and a plurality of pores 42. The pores 42 extend from the outer surface 22 a of the first coating composition 22 to the outer surface 24 a of the second coating composition 24.

The second coating composition can be disposed completely over the first coating composition or the second coating composition can be disposed over a portion of the first coating composition. Additionally the second coating composition can be disposed on the first coating composition in any configuration such as, rings, bands, stripes or dots.

FIG. 5 shows a perspective view of a round stent strut 200 comprising a surface 205 and a coating 210. Coating 210 is disposed on surface 205. Coating 210 comprises a first coating composition 215 comprising a therapeutic agent 220 and a polymer 225 disposed on surface 205 and a second coating composition 230 comprising a metallic material 240 disposed on the first coating composition 215. In this embodiment, the second coating composition 230 is disposed on the first coating composition 215 in the configuration of rings 250.

FIG. 6 shows a perspective view of a square-shaped stent strut 300 comprising a surface 305 and a coating 310. Coating 310 is disposed on surface 305. Coating 310 comprises a first coating composition 315 comprising a therapeutic agent 320 and a polymer 325 disposed on surface 305 and a second coating composition 330 comprising a metallic material 340 with pores as discussed above, disposed on the first coating composition 315. In this embodiment, the second coating composition 330 is disposed on the first coating composition 315 in the configuration of bands 350.

In another embodiment, second coating composition can be in the configuration of parallel bands or stripes. FIG. 7 shows a stent strut 400 comprising a surface 405 and a coating 410. Coating 410 is disposed on surface 405. Coating 410 comprises a first coating composition 415 comprising a therapeutic agent 420 and a polymer 425 disposed on surface 405 and a second coating composition 430 comprising a metallic material 440 with pores as discussed above, disposed on the first coating composition 415. In this embodiment, the second coating composition 430 is disposed on the first coating composition 415 in the configuration of parallel bands or stripes 450.

FIG. 8 shows a stent strut 500 comprising a surface 505 and a coating 510. Coating 510 is disposed on surface 505. Coating 510 comprises a first coating composition 515 comprising a therapeutic agent 520 and a polymer 525 disposed on surface 505 and a second coating composition 530 comprising a metallic material 540 with pores as discussed above, disposed on the first coating composition 515. In this embodiment, the second coating composition 530 is disposed on the first coating composition 515 in the configuration of wavy bands or stripes 550.

FIGS. 5-8 show some examples of configurations of the first coating composition and the second coating composition; however, other configurations of the first coating composition and the second coating composition can be used.

Also, in some embodiments, the second coating composition can be disposed on the first coating composition, as well as, the surface of the medical device. FIG. 9 shows a cross-section view of another embodiment of a coating disposed on at least a portion of a medical device. In this embodiment medical device 600 has a surface 605 and coating 610 is disposed on surface 605 of medical device 600. Coating 610 includes a first coating composition 615 comprising a therapeutic agent 620 and optionally a polymer that is disposed on portions of the surface 605 of medical device 600. A second coating composition 630 comprising a metallic material 640 is disposed on the first coating composition 615, as well as on at least a portion of the surface 605 of the medical device 600. As shown in FIG. 9, the second coating composition 630 when disposed on the first coating composition 615 has an outer surface 630 a and a plurality of pores 642. The pores 642 extend from the outer surface 615 a of the first coating composition 615 to the outer surface 630 a of the second coating composition 630.

In still other embodiments, the coating can comprise a first coating composition comprising a therapeutic agent and optionally a polymer disposed on the surface of a medical device, such as an implantable, intravascular stent and second coating composition comprising a metallic material also disposed on the surface of the medical device. FIG. 10 shows a cross-sectional view of an embodiment of a coating disposed on at least a portion of a medical device. In this embodiment medical device 700 has a surface 705 and a coating 710 disposed on the surface 705 of the medical device 700. Coating 710 includes a first coating composition 715 comprising a therapeutic agent 720 and optionally a polymer disposed on the surface 705 of the medical device 700. The coating 710 also includes a second coating composition 730 comprising a metallic material 740 that is also disposed on the surface 705 of the medical device 700. The second coating composition 730 is substantially free of any polymer. In some embodiments, the second coating composition 730 when applied to the surface 705 can but need not include the pores described above. As shown in FIG. 10, when disposed on the surface 705, both the first coating composition 715 and second coating composition 730 can have the same thickness, h.

Alternatively, as shown in FIG. 11, the thicknesses of the first coating composition 715 and the second coating composition 730 when disposed on the surface 705 of the medical device 700 can be different. As shown in FIG. 11, coating 710 has a first coating composition 715 comprising a therapeutic agent 720 and a polymer 725 and a second coating composition 730 comprising a metallic material 740. When the first coating composition 715 comprises a polymer 725, it may be preferable for the thickness, x, of the second coating composition 730 to be greater than the thickness, y, of the first coating composition 715. Having the thickness x of the second coating composition 730, which is substantially free of any polymer, greater than that of the thickness y of the first coating composition prevents the polymer 725 in the first coating composition 715 from contacting the body lumen. This may eliminate possible adverse effects to the body lumen caused by contact with a polymer.

A. Medical Devices

Suitable medical devices for the present invention include, but are not limited to, stents, surgical staples, cochlear implants, embolic coils, catheters, such as central venous catheters and arterial catheters, guidewires, cannulas, cardiac pacemaker leads or lead tips, cardiac defibrillator leads or lead tips, implantable vascular access ports, blood storage bags, blood tubing, vascular or other grafts, intra-aortic balloon pumps, heart valves, cardiovascular sutures, total artificial hearts and ventricular assist pumps, extra-corporeal devices such as blood oxygenators, blood filters, hemodialysis units, hemoperfusion units or plasmapheresis units.

Medical devices which are particularly suitable for the present invention include any stent for medical purposes, which are known to the skilled artisan. Suitable stents include, for example, vascular stents such as self-expanding stents, balloon expandable stents and sheet deployable stents. Examples of self-expanding stents are illustrated in U.S. Pat. Nos. 4,655,771 and 4,954,126 issued to Wallsten and U.S. Pat. No. 5,061,275 issued to Wallsten et al. Examples of appropriate balloon-expandable stents are shown in U.S. Pat. No. 5,449,373 issued to Pinchasik et al. In preferred embodiments, the stent suitable for the present invention is an Express stent. More preferably, the Express stent is an Express™ stent or an Express2™ stent (Boston Scientific, Inc. Natick, Mass.).

The framework of the suitable stents may be formed through various methods as known in the art. The framework may be welded, molded, laser cut, electro-formed, or consist of filaments or fibers which are wound or braided together in order to form a continuous structure.

Medical devices that are suitable for the present invention may be fabricated from metallic, ceramic, polymeric or composite materials or a combination thereof. Preferably, the materials are biocompatible. Metallic material is more preferable. Suitable metallic materials include metals and alloys based on titanium (such as nitinol, nickel titanium alloys, thermo-memory alloy materials); stainless steel; tantalum, nickel-chrome; or certain cobalt alloys including cobalt-chromium-nickel alloys such as Elgiloy® and Phynox®; PERSS (Platinum EnRiched Stainless Steel) and Niobium. Metallic materials also include clad composite filaments, such as those disclosed in WO 94/16646. Preferred, metallic materials include, platinum enriched stainless steel and zirconium and niobium alloys.

Suitable ceramic materials include, but are not limited to, oxides, carbides, or nitrides of the transition elements such as titanium, hafnium, iridium, chromium, aluminum, and zirconium. Silicon based materials, such as silica, may also be used.

Suitable polymeric materials for forming the medical devices may be biostable. Also, the polymeric material may be biodegradable. Suitable polymeric materials include, but are not limited to, styrene isobutylene copolymers, polyetheroxides, polyvinyl alcohol, polyglycolic acid, polylactic acid, polyamides, poly-2-hydroxy-butyrate, polycaprolactone, poly(lactic-co-clycolic)acid, and Teflon.

Polymeric materials may be used for forming the medical device in the present invention include without limitation isobutylene-based polymers, polystyrene-based polymers, polyacrylates, and polyacrylate derivatives, vinyl acetate-based polymers and its copolymers, polyurethane and its copolymers, silicone and its copolymers, ethylene vinyl-acetate, polyethylene terephtalate, thermoplastic elastomers, polyvinyl chloride, polyolefins, cellulosics, polyamides, polyesters, polysulfones, polytetrafluorethylenes, polycarbonates, acrylonitrile butadiene styrene copolymers, acrylics, polylactic acid, polyglycolic acid, polycaprolactone, polylactic acid-polyethylene oxide copolymers, cellulose, collagens, and chitins.

Other polymers that are useful as materials for medical devices include without limitation dacron polyester, poly(ethylene terephthalate), polycarbonate, polymethylmethacrylate, polypropylene, polyalkylene oxalates, polyvinylchloride, polyurethanes, polysiloxanes, nylons, poly(dimethyl siloxane), polycyanoacrylates, polyphosphazenes, poly(amino acids), ethylene glycol I dimethacrylate, poly(methyl methacrylate), poly(2-hydroxyethyl methacrylate), polytetrafluoroethylene poly(HEMA), polyhydroxyalkanoates, polytetrafluorethylene, polycarbonate, poly(glycolide-lactide) co-polymer, polylactic acid, poly(γ-caprolactone), poly(γ-hydroxybutyrate), polydioxanone, poly(γ-ethyl glutamate), polyiminocarbonates, poly(ortho ester), polyanhydrides, alginate, dextran, chitin, cotton, polyglycolic acid, polyurethane, or derivatized versions thereof, i.e., polymers which have been modified to include, for example, attachment sites or cross-linking groups, e.g., RGD, in which the polymers retain their structural integrity while allowing for attachment of cells and molecules, such as proteins, nucleic acids, and the like.

Medical devices may also be made with non-polymeric materials. Examples of useful non-polymeric materials include sterols such as cholesterol, stigmasterol, β-sitosterol, and estradiol; cholesteryl esters such as cholesteryl stearate; C₁₂-C₂₄ fatty acids such as lauric acid, myristic acid, palmitic acid, stearic acid, arachidic acid, behenic acid, and lignoceric acid; C₁₈-C₃₆ mono-, di- and triacylglycerides such as glyceryl monooleate, glyceryl monolinoleate, glyceryl monolaurate, glyceryl monodocosanoate, glyceryl monomyristate, glyceryl monodicenoate, glyceryl dipalmitate, glyceryl didocosanoate, glyceryl dimyristate, glyceryl didecenoate, glyceryl tridocosanoate, glyceryl trimyristate, glyceryl tridecenoate, glycerol tristearate and mixtures thereof; sucrose fatty acid esters such as sucrose distearate and sucrose palmitate; sorbitan fatty acid esters such as sorbitan monostearate, sorbitan monopalmitate and sorbitan tristearate; C₁₆-C₁₈ fatty alcohols such as cetyl alcohol, myristyl alcohol, stearyl alcohol, and cetostearyl alcohol; esters of fatty alcohols and fatty acids such as cetyl palmitate and cetearyl palmitate; anhydrides of fatty acids such as stearic anhydride; phospholipids including phosphatidylcholine (lecithin), phosphatidylserine, phosphatidylethanolamine, phosphatidylinositol, and lysoderivatives thereof; sphingosine and derivatives thereof; sphingomyelins such as stearyl, palmitoyl, and tricosanyl sphingomyelins; ceramides such as stearyl and palmitoyl ceramides; glycosphingolipids; lanolin and lanolin alcohols; and combinations and mixtures thereof. Non-polymeric materials may also include biomaterials such as stem sells, which can be seeded into the medical device prior to implantation. Preferred non-polymeric materials include cholesterol, glyceryl monostearate, glycerol tristearate, stearic acid, stearic anhydride, glyceryl monooleate, glyceryl monolinoleate, and acetylated monoglycerides.

B. Therapeutic Agents

The term “therapeutic agent” as used in the present invention encompasses drugs, genetic materials, and biological materials and can be used interchangeably with “biologically active material”. In one embodiment, the therapeutic agent is an anti-restenotic agent. In other embodiments, the therapeutic agent inhibits smooth muscle cell proliferation, contraction, migration or hyperactivity. Non-limiting examples of suitable therapeutic agent include heparin, heparin derivatives, urokinase, dextrophenylalanine proline arginine chloromethylketone (PPack), enoxaprin, angiopeptin, hirudin, acetylsalicylic acid, tacrolimus, everolimus, zotarolimus, rapamycin (sirolimus), pimecrolimus, amlodipine, doxazosin, glucocorticoids, betamethasone, dexamethasone, prednisolone, corticosterone, budesonide, sulfasalazine, rosiglitazone, mycophenolic acid, mesalamine, paclitaxel, 5-fluorouracil, cisplatin, vinblastine, vincristine, epothilones, methotrexate, azathioprine, adriamycin, mutamycin, endostatin, angiostatin, thymidine kinase inhibitors, cladribine, lidocaine, bupivacaine, ropivacaine, D-Phe-Pro-Arg chloromethyl ketone, platelet receptor antagonists, anti-thrombin antibodies, anti-platelet receptor antibodies, aspirin, dipyridamole, protamine, hirudin, prostaglandin inhibitors, platelet inhibitors, trapidil, liprostin, tick antiplatelet peptides, 5-azacytidine, vascular endothelial growth factors, growth factor receptors, transcriptional activators, translational promoters, antiproliferative agents, growth factor inhibitors, growth factor receptor antagonists, transcriptional repressors, translational repressors, replication inhibitors, inhibitory antibodies, antibodies directed against growth factors, bifunctional molecules consisting of a growth factor and a cytotoxin, bifunctional molecules consisting of an antibody and a cytotoxin, cholesterol lowering agents, vasodilating agents, agents which interfere with endogenous vasoactive mechanisms, antioxidants, probucol, antibiotic agents, penicillin, cefoxitin, oxacillin, tobranycin, angiogenic substances, fibroblast growth factors, estrogen, estradiol (E2), estriol (E3), 17-beta estradiol, digoxin, beta blockers, captopril, enalopril, statins, steroids, vitamins, paclitaxel (as well as its derivatives, analogs or paclitaxel bound to proteins, e.g. Abraxane™) 2′-succinyl-taxol, 2′-succinyl-taxol triethanolamine, 2′-glutaryl-taxol, 2′-glutaryl-taxol triethanolamine salt, 2′-O-ester with N-(dimethylaminoethyl)glutamine, 2′-O-ester with N-(dimethylaminoethyl)glutamide hydrochloride salt, nitroglycerin, nitrous oxides, nitric oxides, antibiotics, aspirins, digitalis, estrogen, estradiol and glycosides. In one embodiment, the therapeutic agent is a smooth muscle cell inhibitor or antibiotic. In a preferred embodiment, the therapeutic agent is taxol (e.g., Taxol®), or its analogs or derivatives. In another preferred embodiment, the therapeutic agent is paclitaxel, or its analogs or derivatives. In yet another preferred embodiment, the therapeutic agent is an antibiotic such as erythromycin, amphotericin, rapamycin, adriamycin, etc.

The term “genetic materials” means DNA or RNA, including, without limitation, of DNA/RNA encoding a useful protein stated below, intended to be inserted into a human body including viral vectors and non-viral vectors.

The term “biological materials” include cells, yeasts, bacteria, proteins, peptides, cytokines and hormones. Examples for peptides and proteins include vascular endothelial growth factor (VEGF), transforming growth factor (TGF), fibroblast growth factor (FGF), epidermal growth factor (EGF), cartilage growth factor (CGF), nerve growth factor (NGF), keratinocyte growth factor (KGF), skeletal growth factor (SGF), osteoblast-derived growth factor (BDGF), hepatocyte growth factor (HGF), insulin-like growth factor (IGF), cytokine growth factors (CGF), platelet-derived growth factor (PDGF), hypoxia inducible factor-1 (HIF-1), stem cell derived factor (SDF), stem cell factor (SCF), endothelial cell growth supplement (ECGS), granulocyte macrophage colony stimulating factor (GM-CSF), growth differentiation factor (GDF), integrin modulating factor (IMF), calmodulin (CaM), thymidine kinase (TK), tumor necrosis factor (TNF), growth hormone (GH), bone morphogenic protein (BMP) (e.g., BMP-2, BMP-3, BMP-4, BMP-5, BMP-6 (Vgr-1), BMP-7 (PO-1), BMP-8, BMP-9, BMP-10, BMP-11, BMP-12, BMP-14, BMP-15, BMP-16, etc.), matrix metalloproteinase (MMP), tissue inhibitor of matrix metalloproteinase (TIMP), cytokines, interleukin (e.g., IL-1, IL-2, IL-3, IL-4, IL-5, IL-6, IL-7, IL-8, IL-9, IL-10, IL-11, IL-12, IL-15, etc.), lymphokines, interferon, integrin, collagen (all types), elastin, fibrillins, fibronectin, vitronectin, laminin, glycosaminoglycans, proteoglycans, transferrin, cytotactin, cell binding domains (e.g., RGD), and tenascin. Currently preferred BMP's are BMP-2, BMP-3, BMP-4, BMP-5, BMP-6, BMP-7. These dimeric proteins can be provided as homodimers, heterodimers, or combinations thereof, alone or together with other molecules. Cells can be of human origin (autologous or allogeneic) or from an animal source (xenogeneic), genetically engineered, if desired, to deliver proteins of interest at the transplant site. The delivery media can be formulated as needed to maintain cell function and viability. Cells include progenitor cells (e.g., endothelial progenitor cells), stem cells (e.g., mesenchymal, hematopoietic, neuronal), stromal cells, parenchymal cells, undifferentiated cells, fibroblasts, macrophage, and satellite cells.

Other non-genetic therapeutic agents include:

-   -   anti-thrombogenic agents such as heparin, heparin derivatives,         urokinase, and PPack (dextrophenylalanine proline arginine         chloromethylketone);     -   anti-proliferative agents such as enoxaprin, angiopeptin, or         monoclonal antibodies capable of blocking smooth muscle cell         proliferation, hirudin, acetylsalicylic acid, tacrolimus,         everolimus, amlodipine and doxazosin;     -   anti-inflammatory agents such as glucocorticoids, betamethasone,         dexamethasone, prednisolone, corticosterone, budesonide,         estrogen, sulfasalazine, rosiglitazone, mycophenolic acid and         mesalamine;     -   anti-neoplastic/anti-proliferative/anti-miotic agents such as         paclitaxel, 5-fluorouracil, cisplatin, vinblastine, vincristine,         epothilones, methotrexate, azathioprine, adriamycin and         mutamycin; endostatin, angiostatin and thymidine kinase         inhibitors, cladribine, taxol and its analogs or derivatives;     -   anesthetic agents such as lidocaine, bupivacaine, and         ropivacaine;     -   anti-coagulants such as D-Phe-Pro-Arg chloromethyl ketone, an         RGD peptide-containing compound, heparin, antithrombin         compounds, platelet receptor antagonists, anti-thrombin         antibodies, anti-platelet receptor antibodies, aspirin (aspirin         is also classified as an analgesic, antipyretic and         anti-inflammatory drug), dipyridamole, protamine, hirudin,         prostaglandin inhibitors, platelet inhibitors, antiplatelet         agents such as trapidil or liprostin and tick antiplatelet         peptides;     -   DNA demethylating drugs such as 5-azacytidine, which is also         categorized as a RNA or DNA metabolite that inhibit cell growth         and induce apoptosis in certain cancer cells;     -   vascular cell growth promoters such as growth factors, vascular         endothelial growth factors (VEGF, all types including VEGF-2),         growth factor receptors, transcriptional activators, and         translational promoters;     -   vascular cell growth inhibitors such as anti-proliferative         agents, growth factor inhibitors, growth factor receptor         antagonists, transcriptional repressors, translational         repressors, replication inhibitors, inhibitory antibodies,         antibodies directed against growth factors, bifunctional         molecules consisting of a growth factor and a cytotoxin,         bifunctional molecules consisting of an antibody and a         cytotoxin;     -   cholesterol-lowering agents, vasodilating agents, and agents         which interfere with endogenous vasoactive mechanisms;     -   anti-oxidants, such as probucol;     -   antibiotic agents, such as penicillin, cefoxitin, oxacillin,         tobranycin, rapamycin (sirolimus);     -   angiogenic substances, such as acidic and basic fibroblast         growth factors, estrogen including estradiol (E2), estriol (E3)         and 17-beta estradiol;     -   drugs for heart failure, such as digoxin, beta-blockers,         angiotensin-converting enzyme (ACE) inhibitors including         captopril and enalopril, statins and related compounds; and     -   macrolides such as sirolimus, everolimus or zotarolimus.

Preferred biological materials include anti-proliferative drugs such as steroids, vitamins, and restenosis-inhibiting agents. Preferred restenosis-inhibiting agents include microtubule stabilizing agents such as Taxol®, paclitaxel (i.e., paclitaxel, paclitaxel analogs, or paclitaxel derivatives, paclitaxel conjugates and mixtures thereof). For example, derivatives suitable for use in the present invention include 2′-succinyl-taxol, 2′-succinyl-taxol triethanolamine, 2′-glutaryl-taxol, 2′-glutaryl-taxol triethanolamine salt, 2′-O-ester with N-(dimethylaminoethyl) glutamine, paclitaxel 2-N-methypyridinium mesylate, and 2′-O-ester with N-(dimethylaminoethyl) glutamide hydrochloride salt. Paclitaxel conjugates suitable for use in the present invention include, paclitaxel conjugated with docosahexanoic acid (DHA), paclitaxel conjugated with a polyglutimate (PG) polymer and paclitaxel poliglumex.

Other suitable therapeutic agents include tacrolimus; halofuginone; inhibitors of HSP90 heat shock proteins such as geldanamycin; microtubule stabilizing agents such as epothilone D; phosphodiesterase inhibitors such as cliostazole; Barkct inhibitors; phospholamban inhibitors; and Serca 2 gene/proteins.

Other preferred therapeutic agents include nitroglycerin, nitrous oxides, nitric oxides, aspirins, digitalis, estrogen derivatives such as estradiol and glycosides.

In one embodiment, the therapeutic agent is capable of altering the cellular metabolism or inhibiting a cell activity, such as protein synthesis, DNA synthesis, spindle fiber formation, cellular proliferation, cell migration, microtubule formation, microfilament formation, extracellular matrix synthesis, extracellular matrix secretion, or increase in cell volume. In another embodiment, the therapeutic agent is capable of inhibiting cell proliferation and/or migration.

In certain embodiments, the therapeutic agents for use in the medical devices of the present invention can be synthesized by methods well known to one skilled in the art. Alternatively, the therapeutic agents can be purchased from chemical and pharmaceutical companies.

In some embodiments, the therapeutic agent comprises at least 1%, at least 5%, at least 10%, at least 20%, at least 30%, at least 40%, at least 50%, at least 60%, at least 70%, at least 80%, at least 90%, at least 95%, at least 97%, at least 99% or more by weight of the coating. When the coating includes a therapeutic agent without a polymer the therapeutic agent is preferably about 90% to about 100% by weight of the coating. When the coating includes a therapeutic agent and a polymer the therapeutic agent is preferably about 1% to about 90% by weight of the coating. Additionally, a combination of therapeutic agents can be used in the coatings of the present invention.

C. Polymers

Polymers suitable for use, optionally, in the coatings preferably are ones that are biocompatible; however, non-biocompatible polymers can be used. Examples of such polymers include, but not limited to, polyurethanes, polyisobutylene and its copolymers, silicones, and polyesters. Other suitable polymers include polyolefins, polyisobutylene, ethylene-alphaolefin copolymers, acrylic polymers and copolymers, vinyl halide polymers and copolymers such as polyvinyl chloride, polyvinyl ethers such as polyvinyl methyl ether, polyvinylidene halides such as polyvinylidene fluoride and polyvinylidene chloride, polyacrylonitrile, polyvinyl ketones, polyvinyl aromatics such as polystyrene, polyvinyl esters such as polyvinyl acetate; copolymers of vinyl monomers, copolymers of vinyl monomers and olefins such as ethylene-methyl methacrylate copolymers, acrylonitrile-styrene copolymers, ABS resins, ethylene-vinyl acetate copolymers, polyamides such as Nylon 66 and polycaprolactone, alkyd resins, polycarbonates, polyoxyethylenes, polyimides, polyethers, epoxy resins, polyurethanes, rayon-triacetate, cellulose, cellulose acetate, cellulose butyrate, cellulose acetate butyrate, cellophane, cellulose nitrate, cellulose propionate, cellulose ethers, carboxymethyl cellulose, collagens, chitins, polylactic acid, polyglycolic acid, and polylactic acid-polyethylene oxide copolymers.

When the polymer is being applied to a part of the medical device, such as a stent, which undergoes mechanical challenges, e.g. expansion and contraction, the polymers are preferably selected from elastomeric polymers such as silicones (e.g. polysiloxanes and substituted polysiloxanes), polyurethanes, thermoplastic elastomers, ethylene vinyl acetate copolymers, polyolefin elastomers, and EPDM rubbers. The polymer is selected to allow the coating to better adhere to the surface of the strut when the stent is subjected to forces or stress. Furthermore, although the coating can be formed by using a single type of polymer, various combinations of polymers can be employed.

Examples of suitable hydrophobic polymers or monomers include, but not limited to, polyolefins, such as polyethylene, polypropylene, poly(1-butene), poly(2-butene), poly(1-pentene), poly(2-pentene), poly(3-methyl-1-pentene), poly(4-methyl-1-pentene), poly(isoprene), poly(4-methyl-1-pentene), ethylene-propylene copolymers, ethylene-propylene-hexadiene copolymers, ethylene-vinyl acetate copolymers, blends of two or more polyolefins and random and block copolymers prepared from two or more different unsaturated monomers; styrene polymers, such as poly(styrene), poly(2-methylstyrene), styrene-acrylonitrile copolymers having less than about 20 mole-percent acrylonitrile, and styrene-2,2,3,3,-tetrafluoropropyl methacrylate copolymers; halogenated hydrocarbon polymers, such as poly(chlorotrifluoroethylene), chlorotrifluoroethylene-tetrafluoroethylene copolymers, poly(hexafluoropropylene), poly(tetrafluoroethylene), tetrafluoroethylene, tetrafluoroethylene-ethylene copolymers, poly(trifluoroethylene), poly(vinyl fluoride), and poly(vinylidene fluoride); vinyl polymers, such as poly(vinyl butyrate), poly(vinyl decanoate), poly(vinyl dodecanoate), poly(vinyl hexadecanoate), poly(vinyl hexanoate), poly(vinyl propionate), poly(vinyl octanoate), poly(heptafluoroisopropoxyethylene), poly(heptafluoroisopropoxy-propylene), and poly(methacrylonitrile); acrylic polymers, such as poly(n-butyl acetate), poly(ethyl acrylate), poly(1-chlorodifluoromethyl)tetrafluoroethyl acrylate, poly di(chlorofluoromethyl)fluoromethyl acrylate, poly(1,1-dihydroheptafluorobutyl acrylate), poly(1,1-dihydropentafluoroisopropyl acrylate), poly(1,1-dihydropentadecafluorooctyl acrylate), poly(heptafluoroisopropyl acrylate), poly 5-(heptafluoroisopropoxy)pentyl acrylate, poly 11-(heptafluoroisopropoxy)undecyl acrylate, poly 2-(heptafluoropropoxy)ethyl acrylate, and poly(nonafluoroisobutyl acrylate); methacrylic polymers, such as poly(benzyl methacrylate), poly(n-butyl methacrylate), poly(isobutyl methacrylate), poly(t-butyl methacrylate), poly(t-butylaminoethyl methacrylate), poly(dodecyl methacrylate), poly(ethyl methacrylate), poly(2-ethylhexyl methacrylate), poly(n-hexyl methacrylate), poly(phenyl methacrylate), poly(n-propyl methacrylate), poly(octadecyl methacrylate), poly(1,1-dihydropentadecafluorooctyl methacrylate), poly(heptafluoroisopropyl methacrylate), poly(heptadecafluorooctyl methacrylate), poly(1-hydrotetrafluoroethyl methacrylate), poly(1,1-dihydrotetrafluoropropyl methacrylate), poly(1-hydrohexafluoroisopropyl methacrylate), and poly(t-nonafluorobutyl methacrylate); polyesters, such a poly(ethylene terephthalate) and poly(butylene terephthalate); condensation type polymers such as and polyurethanes and siloxane-urethane copolymers; polyorganosiloxanes, i.e., polymeric materials characterized by repeating siloxane groups, represented by RaSiO_(4-a/2), where R is a monovalent substituted or unsubstituted hydrocarbon radical and the value of a is 1 or 2; and naturally occurring hydrophobic polymers such as rubber.

Examples of suitable hydrophilic polymers or monomers include, but not limited to; (meth)acrylic acid, or alkaline metal or ammonium salts thereof; (meth)acrylamide; (meth)acrylonitrile; those polymers to which unsaturated dibasic, such as maleic acid and fumaric acid or half esters of these unsaturated dibasic acids, or alkaline metal or ammonium salts of these dibasic adds or half esters, is added; those polymers to which unsaturated sulfonic, such as 2-acrylamido-2-methylpropanesulfonic, 2-(meth)acryloylethanesulfonic acid, or alkaline metal or ammonium salts thereof, is added; and 2-hydroxyethyl(meth)acrylate and 2-hydroxypropyl(meth)acrylate.

Polyvinyl alcohol is also an example of hydrophilic polymer. Polyvinyl alcohol may contain a plurality of hydrophilic groups such as hydroxyl, amido, carboxyl, amino, ammonium or sulfonyl (—SO₃). Hydrophilic polymers also include, but are not limited to, starch, polysaccharides and related cellulosic polymers; polyalkylene glycols and oxides such as the polyethylene oxides; polymerized ethylenically unsaturated carboxylic acids such as acrylic, mathacrylic and maleic acids and partial esters derived from these acids and polyhydric alcohols such as the alkylene glycols; homopolymers and copolymers derived from acrylamide; and homopolymers and copolymers of vinylpyrrolidone.

Other suitable polymers include without limitation: polyurethanes, silicones (e.g., polysiloxanes and substituted polysiloxanes), and polyesters, styrene-isobutylene-copolymers. Other polymers which can be used include ones that can be dissolved and cured or polymerized on the medical device or polymers having relatively low melting points that can be blended with therapeutic agents. Additional suitable polymers include, but are not limited to, thermoplastic elastomers in general, polyolefins, polyisobutylene, ethylene-alphaolefin copolymers, acrylic polymers and copolymers, vinyl halide polymers and copolymers such as polyvinyl chloride, polyvinyl ethers such as polyvinyl methyl ether, polyvinylidene halides such as polyvinylidene fluoride and polyvinylidene chloride, polyacrylonitrile, polyvinyl ketones, polyvinyl aromatics such as polystyrene, polyvinyl esters such as polyvinyl acetate, copolymers of vinyl monomers, copolymers of vinyl monomers and olefins such as ethylene-methyl methacrylate copolymers, acrylonitrile-styrene copolymers, ABS (acrylonitrile-butadiene-styrene) resins, ethylene-vinyl acetate copolymers, polyamides such as Nylon 66 and polycaprolactone, alkyd resins, polycarbonates, polyoxymethylenes, polyimides, polyethers, polyether block amides, epoxy resins, rayon-triacetate, cellulose, cellulose acetate, cellulose butyrate, cellulose acetate butyrate, cellophane, cellulose nitrate, cellulose propionate, cellulose ethers, carboxymethyl cellulose, collagens, chitins, polylactic acid, polyglycolic acid, polylactic acid-polyethylene oxide copolymers, EPDM (ethylene-propylene-diene) rubbers, fluoropolymers, fluorosilicones, polyethylene glycol, polysaccharides, phospholipids, and combinations of the foregoing.

In certain embodiments block-copolymers are preferred for their ability to help create mesostructured and/or mesoporous coatings. In certain embodiments preferred polymers include, but are not limited to, a polyether, Nylon and polyether copolymers such as PEBAX, a polystyrene copolymer, a polyurethane, an ethylene vinyl acetate copolymer, a polyethylene glycol, a fluoropolymer, a polyaniline, a polythiophene, a polypyrrole, a maleated block copolymer, a polymethylmethacrylate, a polyethylenetheraphtalate or a combination thereof.

In some embodiments, when the first coating composition includes a polymer, the polymer comprises at least 5%, at least 10%, at least 20%, at least 30%, at least 40%, at least 50%, at least 60%, at least 70%, at least 80%, at least 90%, at least 95%, at least 97%, at least 99% or more by weight of the coating. Preferably, the polymer is about 1% to about 80% by weight of the first coating composition. More preferably, the polymer is about 60% to about 92% by weight of the first coating composition. Additionally, a combination of polymers can be used in the first coating composition of the present invention.

D. Methods of Making Coatings

The present invention also relates to methods of making a medical device comprising a coating, wherein the coating comprises a first coating composition comprising a therapeutic agent and a second coating composition comprising a metallic material. Optionally the first coating composition can further comprise a polymer. In certain embodiments, the method comprises (a) providing a medical device having a surface, (b) disposing on at least a portion of the surface a first coating composition comprising a therapeutic agent; and (c) disposing on at least a portion of the first coating composition, a second coating composition comprising a metallic material and that is substantially free of any polymer.

In other embodiments, the method of the present invention comprises (a) providing a medical device having a surface, (b) disposing on at least a portion of the surface a first coating composition comprising a therapeutic agent and a polymer; and (c) disposing on at least a portion of the first coating composition, a second coating composition comprising a metallic material and that is substantially free of any polymer.

In such embodiments the first coating composition may be disposed on the surface of a medical device by any suitable method, such as, but not limited to, spraying for example by using a conventional nozzle or ultrasonic nozzle; dipping; rolling; electrostatic deposition; spin coating; plasma deposition; condensation; electrochemical deposition; electrostatic deposition; evaporation; plasma-vapor deposition; cathodic-arc deposition; sputtering; ion implantation; or use of a fluidized bed or a batch process such as, air suspension, pan coating or ultrasonic mist spraying.

The first coating composition can be made by dissolving or dispersing the therapeutic agent solvent to form a solution or suspension and the solution or suspension can be disposed on the surface of a medical device and the solvent can be removed. Alternatively, if the first coating composition includes a polymer, a therapeutic agent and a polymer can be dissolved or dispersed in a solvent to form a solution or suspension and the solution or suspension can be disposed on the surface of a medical device and the solvent can be removed. Also, a therapeutic agent and a polymer may be mixed together until the therapeutic agent is dissolved or dispersed in the polymer and the mixture can then be disposed of the surface of a medical device.

The second coating composition comprising a metallic material can be disposed on the first coating composition by any suitable methods, such as, but not limited to, spraying for example by using a conventional nozzle or ultrasonic nozzle; dipping; rolling; electrostatic deposition; spin coating; plasma deposition; condensation; electrochemical deposition; electrostatic deposition; evaporation; plasma-vapor deposition; cathodic-arc deposition; sputtering; ion implantation; or use of a fluidized bed or a batch process such as, air suspension, pan coating, ultrasonic mist spraying or thermal spraying.

Prior to deposition, the metallic material in the second coating composition can be placed into a solution or suspension to facilitate deposition. Solutions can be formed using suitable solvents and metallic compounds. Suspensions can be formed by mixing metallic powders with solvents or polymer binders and solvents.

In certain embodiments, the first coating composition can be disposed on at least a portion of the surface of a medical device and then a second coating composition can be disposed on at least a portion of the first coating composition. In some embodiments, the second coating composition comprising a metallic material can be disposed on the first coating composition, as well as, at least a portion of the surface of the first coating composition. Alternatively, the second coating composition comprising a metallic material can be disposed on at least a portion of the surface of the medical device first and then the first coating composition can be disposed on another portion of the surface of the medical device.

Furthermore, pores can be formed or introduced in the second coating composition comprising a metallic material. Such pores can be introduced by any means known in the art. The pores in some instances can be created by micro-roughing techniques involving the use of reactive plasmas or ion bombardment electrolyte etching. The pores can also be created by other methods such as sand blasting, laser etching or chemical etching. In some instances, the pores can be formed by depositing the second coating composition comprising a metallic material in a particular manner so that pores form in the metallic material. For example, the second coating composition can be made porous by a deposition process such as sputtering and adjusting the deposition condition. Deposition conditions that can be adjusted or varied include, but are not limited to, chamber pressure, substrate temperature, substrate bias, substrate orientation, sputter rate, or a combination thereof.

In an alternative method, the pores may be formed using thermal plasma spraying of a spray composition under certain process parameters that promote the formation of pores.

In addition, pores can be formed by a co-deposition technique. In such a technique the second coating composition comprising a metallic material is combined with a secondary phase material to form a composition. The secondary phase material can be non-metal secondary materials, such as a polymer, that are capable of being leached off, such as polystyrene. The secondary phase material can be in the form of particles such as hollow spheres or chopped tubes of various sizes. The size and shape of the pores formed will be determined by the size and shape of the secondary phase material. For example, if the secondary phase material is in the shape of a sphere, the pores formed will be in the shape of spheres.

In some embodiments, the secondary phase material can be a second metallic material. The two metallic materials can form an alloy such as a gold/silver alloy, where gold is the metal used as the metallic material in the second coating composition and silver is the secondary phase material. Also, the two metals can be in the form of a mixture or a composite. Thus, if two metals are used in the composition, the metals should have different chemical or physical properties to facilitate removal of the metal that is used as the secondary phase material. For example, the metal that will be removed should be more electrochemically active, e.g., less corrosion-resistant than the metal used to form the porous coating. In some embodiments, the metal that will be removed should have a lower melting point than the metal used to form the second coating composition. In yet another embodiment, the metal that will be removed should have a higher vapor pressure than the metal used to form the coating. Also, in another embodiment, the metal that is removed is more susceptible to being dissolved in a chosen solvent than the metal used to form the coating.

A composition containing the second coating composition comprising a metallic material and a secondary phase material is applied to the surface of the medical device. Suitable application methods include but are not limited to, dipping, spraying, painting, electroplating, evaporation, plasma vapor deposition, cathodic arc deposition, sputtering, ion implantation, electrostatically, electroplating, electrochemically, or a combination thereof.

Afterwards, the secondary phase material is removed from the composition to form a porous second coating composition. For example, the secondary phase material may be removed from the composition by a dealloying process such as selective dissolution of the secondary phase material. In this method, the composition is exposed to an acid which removes the secondary phase material. Thus, the metallic material used to form the second coating composition is preferably one that will not dissolve when exposed to the acid, while the secondary phase material is one that will dissolve in the acid. Any suitable acid can be used to remove the secondary phase material. One of ordinary skill in the art would recognize the appropriate concentration and reaction conditions to use. For example, if the secondary phase material is silver, nitric acid may be used at a concentration of up to 35% and a temperature up to 120° F. Also, a nitric acid and sulfuric acid mixture (95%/5%) immersion process at 80° F. may be used. The reaction conditions may be varied to vary the geometry, distribution, and depth of the coating.

Alternatively, the second metal can be removed anodically. For example, when silver is used as the secondary phase material, the silver may be removed from the composition applied to the surface anodically using a dilute nitric acid bath comprising up to 15% nitric acid, wherein the anode is the medical device, and the cathode comprises platinum. Voltages up to 10V DC can be applied across the electrodes. The bath chemistry, temperature, applied voltage, and process time may be varied to vary the geometry, distribution, and depth of the coating.

Furthermore, if the secondary phase material has a lower melting point than the metallic material used in the second coating composition, the device coated with the composition containing the second coating composition comprising a metallic material and the secondary phase material can be heated to a temperature such that the secondary phase material becomes a liquid and is removable from the second coating composition. Examples of suitable metals for the second coating composition include one of the higher melting point first metals: platinum, gold, stainless steel, titanium, tantalum, and iridium, in combination with a lower melting point secondary phase material such as: aluminum, barium, and bismuth.

In another embodiment, the secondary phase material has a higher vapor pressure than the second coating composition comprising a metallic material. When the composition applied to the surface of the medical device is heated under vacuum the secondary phase material becomes vaporized and is removed from the second coating composition.

The description contained herein is for purposes of illustration and not for purposes of limitation. Changes and modifications may be made to the embodiments of the description and still be within the scope of the invention. Furthermore, obvious changes, modifications or variations will occur to those skilled in the art. Also, all references cited above are incorporated herein, in their entirety, for all purposes related to this disclosure. 

What is claimed:
 1. An implantable intravascular stent comprising: (a) a stent sidewall structure defining a surface; and (b) a coating comprising (i) a first coating composition formed of a material selected from the group consisting of one or more therapeutic agents and one or more polymers, the first coating composition contacting at least a portion of the surface of the stent sidewall structure wherein the first coating composition has a first thickness measured from the surface of the stent sidewall structure; and (ii) a second coating composition comprising a material different from the first coating composition, the second coating composition comprising a metallic material and being substantially free of any polymer, the second coating contacting at least a portion of the surface of the stent sidewall structure, at least a portion of the second coating composition being disposed adjacent to the first coating composition on the surface of the stent sidewall structure, wherein the second coating composition has a second thickness measured from the surface of the stent sidewall structure; and wherein the second thickness of the second coating composition is the same as or greater than the first thickness of the first coating composition, with the proviso that the second coating composition does not overcoat the first coating composition and at least a portion of the first coating composition remains exposed.
 2. The stent of claim 1, wherein the second coating composition is disposed upon less than all of the outer surface of the first coating composition.
 3. The stent of claim 1, wherein the surface of the stent sidewall structure is an abluminal surface.
 4. The stent of claim 1, wherein the stent sidewall structure comprises a plurality of struts and openings and the surface of the stent sidewall structure is the abluminal surface of the stent.
 5. The stent of claim 4, wherein the surface of the stent sidewall structure is the abluminal surface of at least one of the struts.
 6. The stent of claim 5, wherein the first coating composition and the second coating composition are disposed upon at least a portion of the adluminal surface of at least one of the struts.
 7. The stent of claim 1, wherein the one or more therapeutic agents comprise an agent that inhibits smooth muscle cell proliferation.
 8. The stent of claim 1, wherein the one or more therapeutic agents comprise an antithrombogenic agent, anti-angiogenesis agent, anti-proliferative agent, antibiotic, antirestenosis agent, growth factor, immunosuppressant or radiochemical.
 9. The stent of claim 1, wherein the one or more therapeutic agents comprise an antirestenosis agent.
 10. The stent of claim 1, wherein the one or more therapeutic agents comprise paclitaxel.
 11. The stent of claim 1, wherein the one or more therapeutic agents comprise sirolimus, tacrolimus, pimecrolimus, everolimus or zotarolimus.
 12. The stent of claim 1, wherein the metallic material is selected from the group consisting of stainless steel, nickel, titanium, chromium and alloys thereof.
 13. The stent of claim 1, wherein the one or more polymers are selected from the group consisting of styrene-isobutylene copolymer, polylactic acid, poly(methylmethacrylatebutylacrylate-methylmethacrylate).
 14. The stent of claim 1, wherein the first coating composition forms a first layer having a thickness of about 1 to about 30 microns.
 15. The stem of claim 1 wherein the second coating composition forms a second layer having a thickness of about 0.1 to about 50 microns.
 16. The stent of claim 1, wherein the second thickness of the second coating composition is greater than the first thickness of the first coating composition.
 17. The stent of claim 1, wherein the first thickness of the first coating composition is equal to the second thickness of the second coating composition.
 18. The stent of claim 1, wherein the first coating comprises at least one therapeutic agent and at least one polymer.
 19. The stent of claim 4, wherein the first coating composition and the second coating composition are disposed upon at least a portion of the adluminal surface.
 20. The stent of claim 1, wherein the second thickness is relatively greater than the first thickness and the second coating composition of the coating is exposed for contact with a wall of a lumen when the stent is delivered into the lumen, and the first coating composition of the coating has an outer surface substantially restricted from contact with the wall of the lumen when the stent is delivered into the lumen.
 21. The stent of claim 20, wherein the second coating composition is disposed upon at least a portion of the outer surface of the first coating composition.
 22. The stent of claim 1, with the proviso that no portion of the second coating composition overcoats the first coating composition. 